Sunday, 27 July 2014

The ALPS VCO 1679C is operational. Power supply and tuning voltage have been connected now. Also a small MMIC, the MSA-0866 from Hewlett Packard has been connected to the output to increase the output level from about 0 dBm to abt. 12 dBm. I viewed the spectrum on the SDR receiver and found I could generate a stable signal in the 23 cm band. Here you see a clean signal around 1.256 GHz:

The VCO can be tuned between 1100 and 1350 MHz. I think the long and short term stability are good enough to use the free running VCO for 23 cm ATV transmission. No PLL required !

Friday, 18 July 2014

In my post of June 29, I described a trial to make an oscillator which generates an EM-signal with a frequency higher than 1 GHz. The circuit, in which a BFR96 was used, did work, but the oscillator appeared to be rather unstable. Certainly not stable enough to form the core of a simple 23 cm FM TV transmitter I want to design. Also I do not want to waste time trying to make the design stable by using frequency divider/PLL circuitry. My experience with PLL circuits is not very good.In my search on the internet for a stable VCO, I found the ALPS 1679C at Kingcom and ordered one ( kingcom(at)chello.nl ). This VCO has a frequency range of 1100 - 1350 MHz. This covers the 23 cm HAM band (1240 - 1300 MHz). The VCO provides 1 mW RF output (0 dBm into 50 ohms).I am curious to find out how this little device behaves.

With a simple dipole antenna it was easy to improve the receive results of the ADS-B receiver. I soldered two elements of about 6 cm to a coaxcable which is connected to the TVdongle. Results were great:With DVB-T antenna; Less than 10 aircraft: DVB-T antenna (not tuned to 1090 MHz)

Saturday, 5 July 2014

No hot solder iron required for this project. This morning, I have been able to capture aircraft flying above me by receiving theirADS-B 1090 MHz signal. For this purpose the SDRsharp dongle is used. See my blog article of 7 June. All the "ins" and "outs" of ADS-B (Automatic Dependent Surveillance Broadcast) can be found on the internet. For example here: http://nl.wikipedia.org/wiki/ADS-BI followed the intructions of the "Sterrenwacht Leeuwarden" and installed "RTL1090 beta 3" and "Globestrl" succesfully.http://www.sterrenwachtleeuwarden.nl/adsb%20ADS-B%20luchtvaart%20radar.htmlNow I can watch "real-time", without internet connection, the aircraft flying above thewestern part of The Netherlands:

RTL1090 Beta3 version

Globe-S, aircraft trajectories on July 5 abt 14:00 hr local time

On top of my PC on the righthand side you see the small antenna (which is designed for television DVB-T reception) and the RTLsdr dongle inserted in the upper USB port

Interesting to see how an ADS-B signal looks like in the frequency domain: